The aim of this work was to study the prevalence of Q-T prolongation in patients with liver cirrhosis and the modifications of the Q-T interval after liver transplantation. Q-T interval corrected for heart rate (QT_c) and dispersion of Q-T interval were evaluated in 75 cirrhotic patients and in 24 controls by means of a 12-lead electrocardiogram. In addition, 15 patients were evaluated before and after liver transplantation. Forty-five patients (60%) had a prolonged Q-T_c. Compared with controls, both patients with alcoholic and non alcoholic cirrhosis had increased Q-T_c (414±28 msec^1/2, 463±31 and 444±32 respectively; p<0.001 and <0.001); Q-T_c was significantly higher in alcoholic than in non-alcoholic cirrhosis (p<0.02). Q-T dispersion was normal in cirrhotics. No correlation was found between Q-T_c interval and severity of the cirrhosis, haemodynamic variables (stroke volume, cardiac output) and s-calcium and potassium concentrations. After transplantation, Q-T_c decreased significantly (415±26 msec_1/2 vs 449±31; p<0.0001) returning to the values of the normal subjects, but no modification of the Q-T dispersion was observed. These data show that 1) prolongation of Q-T interval is frequent in cirrhosis, being higher in alcoholic than in non-alcoholic cirrhosis, 2) is not related to the severity of the disease, and 3) is reversible after transplantation.